Chronic MTX treatment had no effect on established tumor immunity, but prevented the development of the primary immune response to tumor. Adoptive transfer of tumor immunity was insensitive to MTX treatment indicating that the primary cell-medicated response of the recipient was not required for effective transfer. The efficacy of adoptive immunity was evaluated in guinea pigs depleted of T cells. Despite demonstrable deficiency in T cell reactions, "B" guinea pigs were capable of rejecting tumor after adoptive transfer. These results suggest that expression of adoptive immunity was independent of recipient T cell function. Evidence for the participation of recipient components other than T cells was obtained using the inhibitors carrageenan and trypan blue.